1. Field of the Invention
The present Invention relates to a method of producing fibriform silicon nitride, and more specifically, to a method of manufacturing silicon nitride whiskers having a long size.
2. Description of the Prior Art
A silicon carbide (SiC) material is known as a structural material, and when compared wlth this, a silicon nitride (Si.sub.3 N.sub.4) material is excellent in corrosion resistance, abrasion resistance,,heat resistance and mechanical strength and has been widely used as a dispersion reinforcement. Therefore, it is wise to use the silicon nitride material for reinforcement of a silicon carbide material in order to obtain an improved structural material able to endure to high temperature. On the other hand, in the field of structural materials, fiber reinforced ceramics has been known as promising structural materials, and it is therefore retarded that fiber reinforcements may be useful. In the above circumstances, there is a need for a fibriform silicon nitride material has arised.
With regard to silicon nitride powder, various manufacturing methods have been achieved, and typical one is disclosed by V. Vanedenede, A. Leriche, F. Cambier, H. Pickup, and R. J. Brook in "Sinterability of Silicon Nitride Powders and Characterization of Sintered Material", pp.53-67 in Non-oxide Technical and Engineering Ceramics, Edited by S. Hampshire. Elservier, London, 1986. However, with respect to the formation of fibriform silicon nitride, only a few studies have been conducted, which are, for example, disclosed by U. Saito, Th Hayashi and K. Miura in "Effect of Fluorides on Vapor Phase Browth of Silicon Nitride Whiskers", Nippon Kagaku Kaishi, 401(1982); and by T. Hayashi, S. Kawabe and H. Saito in "Vapor Phase Growth of .beta.-Sialon Whisker by Nitridation of the System SiO.sub.2 --C--Na.sub.3 AlF.sub.6 ", Yogyu Kyokaishi, 94, 19(1986). At the present time, only production of silicon nitride whiskers having a length of only 200 .mu.m is known and such whiskers have already been supplied commercially. However. a method for producing long silicon nitride whiskers such as those having a length more than 10 mm has not yet been discovered.